Constantly increasing demands of users motivates rapid development of mobile communication technologies. Currently, fifth generation (5G) millimeter-wave networks are being actively developed. The 5G millimeter-wave networks may require higher performance based on user experience and including such factors as ease of connectivity with nearby devices and improved energy efficiency. Millimeter-wave technologies encounter a variety of fundamental challenges, which are associated with physics of antenna arrays, structure of a high-speed transceiver, and the like.
Still remaining main tasks for integration of millimeter-wave antennas are to reduce cost, decrease interference level, and provide required communication quality and energy efficiency. Further, a communication channel shall maintain stability when a communicating mobile device changes its position. Accordingly, the following requirements may be imposed on e.g., antennas of base stations:
1) high gain,
2) wide scan angles,
3) high directivity,
4) low sidelobe level,
5) dual-polarized beamforming to increase rate and improve stability of data transmission, and
6) high efficiency of the antenna.
FIG. 1 shows configuration of antennas in a base station according to the related art.
Referring to FIG. 1, a very important task in operation of scanning antennas is to increase the scan angle, which in turn may enhance the efficiency of the system. The scan angle of a traditional antenna array is generally restricted by ±45 degrees in order not to cause a significant reduction in gain and an excessive increase in the sidelobe level. Therefore, as shown in FIG. 1, in configuring a traditional base station (or BS), four antennas BSA1, BSA2, BSA3, and BSA4 each having a scan angle of ±45 degrees, may be arranged to cover an area of 360 degrees around the base station. The use of three antennas instead of four, to cover the entire coverage area (i.e., to provide a desired level of waves for the entire coverage area), could significantly alleviate requirements for the complexity of control and distribution devices on the side of the base station transceiver, decrease the base station dimensions, and simplify and speed up installation of the base station. Therefore, to configure a base station with three antennas, it would be desirable that each of the three antennas has a scan angle of more than ±60 degrees not less than ±60 degrees.
To expand the scan angle in the millimeter-wave communication frequency range, special means may be required. For example, a conformal antenna array (cylindrical type), Luneburg lens antennas, and switched axisymmetric antennas are currently used for increasing the scan angle. These types of antennas may provide a scan angle of ±90 and more. However, they have some disadvantages: namely, they include a sophisticated switching unit that introduces additional loss, require large spatial dimensions, and have low efficiency of the antenna aperture.
Traditional antenna arrays may obtain an extended scanning beam by means of special structures installed in front of the array. These structures may cause additional deviation of the wave front, and are generally used for large broad-side arrays.
There are some millimeter-wave solutions that approach the aforementioned requirements to some extent according to the related art.
FIGS. 2, 3, 4, and 5 show examples of millimeter-wave antennas according to the related art.
Referring to FIG. 2, the publication “An E-band Cylindrical Reflector Antenna for Wireless Communication Systems” 7th European Conference on Antennas and Propagation (EUCAP2013)” discloses a cylindrical reflector antenna designed for high frequency applications and having a high gain and relatively low losses. However, this antenna is incapable of scanning, has an efficiency of about 60% and operates with a single polarization only.
Referring to FIG. 3, another antenna of the related art for application at 23 GHz frequencies is disclosed in the publication “Cylindrical-parabolic reflector with printed antenna structures” IHTM-CMTM, University of Belgrade Journal of Microelectronics, Electronic Components and Materials, Vol. 43, No. 2(2013), 97-102. The disclosed antenna has a radiating structure in the form of a microstrip antenna array of dipoles, and a cylindrical reflector. Like the previous example, this antenna has no scanning ability and operates with a single polarization only. Furthermore, a microstrip feeder of the antenna disclosed by the university of Belgrade journal operates with an efficiency of only 56% because the losses in feeding radiators reach 2-3 dB. In the millimeter-wave communication, the losses in the microstrip feeder may further increase due to dielectric material loss and manufacturing defects (any irregularities, thickening, narrowing, notches, curvatures, corners, etc. may cause re-reflection, parasitic radiation, etc.). Therefore, the distributed system of the feeder path may be a disadvantage for millimeter antennas.
Referring to FIG. 4, another antenna of the related art is disclosed in the publication “The Design on the Antenna Array with High Gain and Scanning Beam” Lu Zhiyong, the 54th Research Institute of CETC, Shijiazhuang, 050081, China, International Conference on Microwave and Millimeter Wave Technology (ICMMT), 2012. A cylindrical (parabolic) reflector is illuminated by a special array to form a scanning beam. This antenna, like the previous antennas, operates with a single polarization and has a relatively low efficiency (about 60%). Furthermore, the antenna has a very limited scan angle (±20 degrees), so nine antennas are required to cover an area of 360 degrees, and given its extreme complexity, the use of such an antenna in base stations for mobile communications is hardly suitable.
Referring to FIG. 5, as another millimeter-wave antenna, Thomson CSF Radar Maser-T antenna has been proposed. The antenna is a complex scanning antenna array consisting of a plurality of linear microstrip antenna arrays, and the scanning antennas are connected to the respective transceiver circuits. However, despite all the complexity, this antenna is restricted by a scan angle of ±40 degrees, and its microstrip structure may cause high loss in the feeder lines and low antenna efficiency.
Such technologies of the related art are not suitable for providing antenna devices, which could simultaneously meet all of the above requirements.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.